Peroxyester preparation method

ABSTRACT

The present invention relates to a process for the preparation of a peroxyester which can be used in particular in polymerizations, such as the polymerization of vinyl chloride, or in the thermosetting of polyester resins. 
     This process comprises the reaction of a hydroxyhydroperoxide salt with an acid halide or an acid anhydride under the following conditions:
         the molar ratio R b  of the hydroxyhydroperoxide corresponding to the hydroxyhydroperoxide salt to the acid halide is between 0.5 and 1.5; or alternatively the molar ratio R b ′ of the hydroxyhydroperoxide corresponding to the hydroxyhydroperoxide salt to the acid anhydride is between 1.0 and 3.0;   the hydroxyhydroperoxide salt was prepared beforehand by reaction of the corresponding hydroxyhydroperoxide with a base according to a molar ratio R a  of the base to the hydroxyhydroperoxide of between 0.5 and 1.5; and   this process is carried out in aqueous media.       

     The invention also relates to an aqueous emulsion comprising the peroxyester obtained and to a polymerization process employing a radical initiator comprising this peroxyester.

The present invention relates to a process for the preparation of aperoxyester which can be used in particular in polymerizations, such asthe polymerization of vinyl chloride, or in the thermosetting ofpolyester resins.

Numerous documents of the prior art mention the preparation ofperoxyesters:

-   -   European Patent Application No. 667 339, which relates to        unsaturated peroxides and to polymers obtained using these        peroxides;    -   European Patent Application No. 126 216, which relates to        hydroxy-t-alkyl peroxyesters having 10-hour half-life        temperatures of less than 75° C.;    -   U.S. Pat. No. 3,624,124, which relates to tertiary hydroperoxide        and tertiary alkyl peresters;    -   European Patent Application No. 381 135, which discloses        hydroxyperoxides having 10-hour half-life temperatures of        between 85 and 100° C.; and    -   European Patent Application No. 474 227, which relates to        functionalized peroxides intended for polymerization reactions.

However, in all these documents, the peroxyesters are prepared in thepresence of a solvent and sometimes of a phase transfer catalyst.

During the preparation of peroxyesters having a hydroxyl group in the γposition with respect to the O—O peroxide functional group, problems ofdecanting, that is to say of poor separation of the organic phase and ofthe aqueous phase, may be encountered.

To overcome these problems, use is then made of a solvent which makes itpossible to accelerate the phenomenon of decanting; however, thissolvent poses an additional problem: part of it remains in theperoxyester, which is a nuisance during the use of the peroxyesterbecause of the subsequent presence of solvent in the polymer.

Another solution consists in patiently waiting for the decanting to takeplace unaided, which can take several days.

It has now been discovered that it is possible to obtain rapid decantingwithout having recourse to a solvent.

A subject-matter of the invention is therefore a process for thepreparation of a peroxyester comprising the reaction of ahydroxyhydroperoxide salt with an acid halide or an acid anhydride, inwhich:

-   -   the molar ratio R_(b) of the hydroxyhydroperoxide corresponding        to the hydroxyhydroperoxide salt to the acid halide is between        0.5 and 1.5; or alternatively the molar ratio R_(b)′ of the        hydroxyhydroperoxide corresponding to the hydroxyhydroperoxide        salt to the acid anhydride is between 1.0 and 3.0;    -   the hydroxyhydroperoxide salt was prepared beforehand by        reaction of the corresponding hydroxyhydroperoxide with a base        according to a molar ratio R_(a) of the base to the        hydroxyhydroperoxide of between 0.5 and 1.5; and    -   this process is carried out in aqueous media.

Such a process therefore offers the following advantages:

-   -   the reaction of the hydroperoxide salt with the acid halide or        anhydride can now be carried out in the absence of organic        solvent and, if appropriate, of phase transfer catalyst;    -   the decanting takes place rapidly, which, first, makes possible        a saving in time and, secondly, avoids the need to store certain        rather unstable peroxyesters in low-temperature storage areas;    -   the peroxyester obtained is devoid of any solvent; any        subsequent stage of evaporation or distillation of the solvent        is thus avoided, which improves the yield;    -   the purity of the peroxyester obtained is satisfactory;    -   the absence of solvent additionally eliminates the risk of        introducing, into the peroxyester or the final product, possible        impurities present in the solvent;    -   the peroxyester can be used as obtained, that is to say without        subsequent purification, without the occurrence, for example,        during use in polymerization reactions, of side reactions, such        as transfer reactions, or problems of colour or smell of the        polymer obtained.

Another subject-matter of the invention is an aqueous emulsioncomprising at least one peroxyester obtained by the process according tothe invention.

Another subject-matter of the invention is a polymerization processemploying a radical initiator comprising at least one peroxyesterobtained by the process according to the invention.

Other characteristics and advantages of the invention will becomeapparent on reading the description which follows and which isillustrated by examples.

DETAILED DESCRIPTION OF THE INVENTION

The preparation process according to the invention can therefore becarried out in the aqueous phase.

It can comprise a preliminary stage of preparation of the hydroperoxidesalt by reaction of a hydroperoxide with a base.

Thus, the synthesis of the peroxyester can be illustrated by thefollowing reaction scheme:

-   -   Stage a):    -   ROOH+base→ROOM    -   Stage b):    -   R′C(O)X or (R′CO)₂O+ROOM→R′—C(O)—O—O—R    -   in which:    -   ROOH is a hydroperoxide;    -   ROOM is a salt of the hydroperoxide;    -   R′C(O)X is an acid halide;    -   (R′CO)₂O is an acid anhydride.

One advantage of the process according to the invention is that stage b)can be carried out in the reactor which has been used to carry out stagea).

Stage a)

The starting hydroperoxide ROOH can be any hydroperoxide. It ispreferably a hydroxyhydroperoxide.

Use is in particular made, as hydroxyhydroperoxides, of those in whichthe hydroxyl group is situated in the 3 position with respect to thehydroperoxy group.

In addition, it is preferable to use hydroxy(tertiary-alkyl)hydroperoxides.

Mention may be made, as examples of such compounds, of thosecorresponding to the following general formula:HO—C(R₃)(R₄)—CH₂—C(R₁)(R₂)—OOH

-   -   in which:    -   R₁ and R₂ are, independently of one another, an alkyl having        from 1 to 4 carbon atoms;    -   R₃ and R₄ are, independently of one another, a hydrogen or an        alkyl having from 1 to 4 carbon atoms;    -   R₁ and R₃ can be connected to one another via an alkylene bridge        having 3 carbon atoms, this bridge optionally being substituted        by an alkyl having from 1 to 4 carbon atoms; and R₃ can        additionally be a —CH₂—C(R₁) (R₂)—OOH group, R₁ and R₂ being as        defined above.

Mention may be made, as hydroxy(t-alkyl) hydroperoxides, of3-hydroxy-1,1-dimethylpropyl, 3-hydroxy-1,1-dimethylbutyl,1-ethyl-3-hydroxy-1-methylpentyl, 1,1-diethyl-3-hydroxybutyl and5-hydroxy-1,3,3-trimethylcyclohexyl hydroperoxides.

According to the invention, the preferred hydroxyhydroperoxides arehexylene glycol hydroperoxides, in particular3-hydroxy-1,1-dimethylbutyl hydroperoxide.

These hydroxy(t-alkyl) hydroperoxides can be prepared by treating thecorresponding hydroxy (t-alcohols) with an excess of hydrogen peroxidein the presence of a highly acidic catalyst, such as sulphuric acid,phosphoric acid, perchloric acid or p-toluenesulphonic acid.

For example, hexylene glycol hydroperoxide can be prepared in this wayfrom commercial hexylene glycol according to the teachings of U.S. Pat.No. 336,872.

The hydroxy(t-alcohols) can in their turn be prepared in a known way.

Use may be made, as base for stage a) of the process, of inorganicbases, such as NaOH, KOH, LiOH, Na₂CO₃, K₂CO₃, NaHCO₃, KHCO₃, Ca(OH)₂,Ba(OH)₂, CaCO₃ or Na₃PO₄, or alternatively of organic bases, such asamines, for example pyridine, N,N-dimethylaniline,4-(N,N-dimethyl-amino)pyridine, triethylamine, tributylamine,1azabicyclo[2.2.2]octane, 1,4-diazabicyclo[2.2.2]octane,1,8-diazabicyclo[5.3.0]undec-7-ene, urea and tetramethyl-urea.

Use is preferably made of a base, in particular potassium hydroxide orsodium hydroxide. Potassium hydroxide is the preferred base.

The molar ratio R_(a) of the base to the hydroperoxide is generallybetween 0.5 and 1.5.

According to another advantageous embodiment of the invention, the molarratio R_(a) is between 0.9 and 1.3, preferably between 1.00 and 1.22 andin particular between 1.10 and 1.19.

Stage a) is generally carried out at a temperature of 20-25° C., thehydroxyhydroperoxide generally being reacted as is (in the substantiallypure state and without prior dissolution in an organic solvent),gradually, with stirring, with the organic base, the latter optionallybeing in the form of an aqueous solution.

The reaction mixture is then generally kept stirred for a few minutes inorder to bring the formation of the hydroxyhydroperoxide salt tocompletion.

Stage b)

This stage is carried out between the hydroperoxide salt obtained oncompletion of stage a) and either an acid anhydride or an acid halide.

The acid anhydride can be chosen from the group consisting of theanhydrides of 2-methoxypropionic, isobutyric, tert-butyric, pivalic,2,2-dimethylbutyric, 2-ethylbutyric, hexanoic, neohexanoic, benzoic,heptanoic, neoheptanoic, 2-ethylhexanoic, octanoic, neooctanoic,2-phenoxypropanoic, 2-phenylpropanoic, nonanoic, isononanoic,neononanoic, 2-methyl-2-phenylpropionic, 2-phenylbutyric, decanoic,neodecanoic, dodecanoic, 2-butyloctanoic, neododecanoic, undecanoic,neotridecanoic, methacrylic, methylcrotonic and 2-methyl-2-butenoicacids.

According to a preferred embodiment of the invention, stage b) iscarried out with an acid halide.

This acid halide generally has, as empirical formula, the formula R′COX,in which:

-   -   R′ corresponds to one of the following formulae:        R₅R₆R₇C— and R₉CH═CR₈—    -   in which:    -   R₅ is a hydrogen or an alkyl having from 1 to 8 carbon atoms;    -   R₆ is an alkyl having from 1 to 8 carbon atoms;    -   R₇ is an alkyl having from 1 to 8 carbon atoms, an alkenyl        having from 2 to 8 carbon atoms, an aryl having from 6 to 10        carbon atoms, an alkoxy having from 1 to 6 carbon atoms or an        aryloxy having from 6 to 10 carbon atoms;    -   R₈ and R₉ are, independently of one another, an alkyl having        from 1 to 4 carbon atoms; and    -   X is a halogen.

Use may thus be made, as acid halides, of 2-methoxypropionyl,isobutyroyl, tert-butyroyl, pivaloyl, 2,2-dimethylbutyroyl,2-ethylbutyroyl, hexanoyl, neohexanoyl, benzoyl, heptanoyl,neoheptanoyl, 2-ethyl-hexanoyl, octanoyle, neooctanoyl,2-phenoxypropanoyl, 2-phenylpropanoyl, nonanoyl, isononanoyl,neononanoyl, 2-methyl-2-phenylpropionyl, 2-phenylbutyroyl, decanoyl,neodecanoyl, dodecanoyl, 2-butyloctanoyl, neododecanoyl, undecanoyl,neotridecanoyl, methacryloyl, methylcrotonoyl and 2-methyl-2-butenoylhalides.

Preferably, the halogen X is a chlorine atom.

According to the invention, the most advantageous acid halide isneodecanoyl chloride with the empirical formula t-C₉H₁₉—COCl.

The acid chlorides can be prepared in a known way, for example from thecorresponding acids, by reaction with chlorinating agents, such as PCl₃,POCl₃, PCl₅, SOCl₂, phosgene (in the presence of N,N-dimethylformamide)or trichlorobenzene, and then by separation of the acid chloride fromthe reaction medium.

According to an advantageous embodiment of the invention, the molarratio R_(b) of the hydroperoxide (corresponding to the hydroperoxidesalt) to the acid halide is between 0.9 and 1.2, preferably between 1.00and 1.17 and in particular between 1.10 and 1.16.

In stage b), the acid anhydride or halide can be added as is (that is tosay, without prior dissolution in an organic solvent) to the saltobtained on completion of stage a), for example over 5 to 60 minutes,preferably over 10 to 20 minutes, and generally with stirring. Thetemperature of the beginning of addition is from 15 to 25° C. andpreferably from 18 to 23° C.

The addition is generally fairly exothermic and there is generally achange from a temperature of 20° C. to 30° C. Subsequently, the reactiontemperature is generally maintained between 20 and 40° C. and preferablybetween 25 and 35° C. Such ranges of reaction temperatures are generallysufficient to produce good reaction kinetics without causing theperoxyester formed to decompose. The reaction time is generally from 10to 90 minutes and preferably from 20 to 40 minutes.

The reaction medium is subsequently treated generally at ambienttemperature.

Various additional stages can be implemented.

A first washing with water is carried out and the aqueous phase isseparated from the organic phase and is then removed from the medium.Another washing with a 3% aqueous potassium hydroxide (or sodiumhydroxide) solution is carried out and the aqueous phase is separatedfrom the organic phase and is then removed from the medium.

A phase transfer catalyst can optionally be used to facilitate theseparation of the phases.

The peroxyester, which is the predominant constituent of the organicphase, is thus obtained.

The organic phase can subsequently be quantitatively determined by aniodometric method to determine the peroxyester content. The watercontent can also be approximately measured by addition of heptane to theorganic phase and then more accurately by a Karl-Fischer method.

Uses

Peroxyesters and in particular 1,1-dimethyl-3-hydroxybutylperoxyneodecanoate have numerous applications in industry.

They can participate, in particular, in polymerization reactions, forexample in the polymerization of vinyl chloride, or in the thermosettingof polyester resins.

Reference may be made to the following documents to find examples ofapplications of peroxyesters:

-   -   International Application No. WO 99/31194, which relates to the        polymerization of vinyl monomers;    -   U.S. Pat. No. 5,612,426, which relates to the production of PVC;    -   Japanese Patent Application No. JP 7258316, which relates to the        suspension polymerization of vinyl chloride;    -   Japanese Patent Application No. JP 7258315, which relates to the        preparation of an aqueous emulsion; and    -   Japanese Patent Applications Nos. JP 7252308 and JP 7252307,        which disclose the preparation of PVC.

EXAMPLES

The following examples illustrate the present invention without,however, limiting the scope thereof.

They describe the synthesis of 1,1-dimethyl-3-hydroxybutylperoxyneodecanoate.

Example 1

A 250 ml jacketed reactor, equipped with a mechanical stirrer and athermometer and connected to an automatically-controlled heating/coolingsystem, is charged with 62.42 g of a 23% aqueous KOH solution.

37.96 g of hexylene glycol hydroperoxide, with a purity of 78%, aregradually added while maintaining the temperature of the reactor at 20°C. The mixture is subsequently stirred for two minutes at 20° C. at astirring rate of 200 revolutions per minute.

36.94 g of neodecanoyl chloride, with a purity of 99.9%, are then addedto the reactor while stirring at 250 revolutions per minute. Thetemperature changes from 20° C. at the beginning of the addition to26.9° C. at the end of the addition.

The automatically-controlled heating/cooling system is subsequentlyadjusted to 30° C. and the reaction mass is stirred for 30 minutes at30° C. at a stirring rate of 250 revolutions per minute.

The automatically-controlled heating/cooling system is then adjusted to20° C., 24.7 g of water are added and the reaction medium is leftstanding for 5 minutes, which makes it possible to remove the aqueousphase from the medium. The medium is subsequently washed with 64.6 g ofa 3% aqueous KOH solution at a stirring rate of 280 revolutions perminute for 5 minutes.

After separating the phases and removing the aqueous phase, 49.1 g of anorganic phase are obtained.

An iodometric analysis makes it possible to measure a peroxyester purityof 91.4%; the product comprises approximately 2.1% of water, which leadsto a product purity of 93.3% (water not being regarded as an impurity).The yield, based on neodecanoyl chloride, is 82.3%.

Example 2

A 250 ml jacketed reactor, equipped with a mechanical stirrer and athermometer and connected to an automatically-controlled heating/coolingsystem, is charged with 62.40 g of a 23% aqueous KOH solution.

38.28 g of hexylene glycol hydroperoxide, with a purity of 75%, aregradually added while maintaining the temperature of the reactor at 20°C. The mixture is subsequently stirred for two minutes at 20° C. at astirring rate of 200 revolutions per minute.

36.93 g of neodecanoyl chloride, with a purity of 95.5%, are then addedto the reactor while stirring at 250 revolutions per minute. Thetemperature changes from 20° C. at the beginning of the addition to30.3° C. at the end of the addition.

The automatically-controlled heating/cooling system is subsequentlyadjusted to 30° C. and the reaction mass is stirred for 30 minutes at30° C. at a stirring rate of 250 revolutions per minute.

Treatment is then carried out with 2 g of 50% hydrogen peroxide and thereaction medium is stirred at 30° C. for 15 minutes.

The automatically-controlled heating/cooling system is subsequentlyadjusted to 20° C., 24.4 g of water are added and the reaction medium isleft standing for 5 minutes, which makes it possible to remove theaqueous phase from the medium. The medium is subsequently washed with64.9 g of a 3% aqueous KOH solution at a stirring rate of 280revolutions per minute for 5 minutes.

After separating the phases and removing the aqueous phase, 44.9 g of anorganic phase are obtained.

An iodometric analysis makes it possible to measure a peroxyester purityof 78.2%; the product comprises approximately 8.9% of water, which leadsto a product purity of 85.9% (water not being regarded as an impurity).The yield, based on neodecanoyl chloride, is 72.2%.

Example 3 (Comparative)

A 250 ml jacketed reactor, equipped with a mechanical stirrer and athermometer and connected to an automatically-controlled heating/coolingsystem, is charged with 65 g of a 30% aqueous KOH solution.

36.88 g of hexylene glycol hydroperoxide, with a purity of 78%, aregradually added while maintaining the temperature of the reactor at 20°C. The mixture is subsequently stirred for two minutes at 20° C. at astirring rate of 200 revolutions per minute.

36.94 g of neodecanoyl chloride, with a purity of 99.9%, are then addedto the reactor while stirring at 250 revolutions per minute. Thetemperature changes from 20° C. at the beginning of the addition to 28°C. at the end of the addition.

The automatically-controlled heating/cooling system is subsequentlyadjusted to 30° C. and the reaction mass is stirred for 30 minutes at30° C. at a stirring rate of 250 revolutions per minute.

The automatically-controlled heating/cooling system is subsequentlyadjusted to 20° C., 24.5 g of water are added and the reaction medium isleft standing for 5 minutes, which makes it possible to remove theaqueous phase from the medium. The medium is subsequently washed with64.6 g of a 3% aqueous KOH solution at a stirring rate of 280revolutions per minute for 5 minutes.

No separation of the phases is observed.

1. A process for the preparation of a peroxyester said processcomprising conducting the following sequential steps: (a) reacting anhydroxyhydroperoxide with a base in the absence of an organic solvent,and with a molar ratio R_(a) of the base to the hydroperoxide of between0.9 and 1.3, to obtain a salt of the hydroxyhydroperoxide, (b) oncompletion of step (a) reacting resultant salt of hydroxyhydroperoxidewith an acid chloride or an acid anhydride in the absence of an organicsolvent to form a peroxyester, wherein the mol ratio R_(b) of thehydroxyhydroperoxide corresponding to the salt to the acid halide isbetween 0.5 and 1.5 or the mol ratio R_(b) of the hydroxyhydroperoxidecorresponding to the hydroxyhydroperoxide salt to the acid anhydride isbetween 1.0 and 3.0, (c) recovering said peroxyester from step (b) so asto produce a final product, said recovery being conducted in the absenceof an organic solvent, and wherein the hydroxyhydroperoxide is ahydroxy(tertiary-alkyl) hydroperoxide in which the hydroxyl group issituated in the 3 position with respect to the hydroperoxy group.
 2. Aprocess according to claim 1 wherein the mol ratio R_(a) is between 1.0and 1.22.
 3. A process according to claim 1 wherein the mol ratio R_(a)is between 1.10 and 1.19.
 4. A process for the preparation of aperoxyester said process comprising conducting the following sequentialsteps: (a) reacting an hydroxyhydroperoxide with a base in the absenceof an organic solvent, and with a molar ratio R_(a) of the base to thehydroperoxide of between 0.9 and 1.3, to obtain a salt of thehydroxyhydroperoxide, (b) on completion of step (a) reacting resultantsalt of hydroxyhydroperoxide with an acid chloride or an acid anhydridein the absence of an organic solvent to form a peroxyester, wherein themol ratio R_(b) of the hydroxyhydroperoxide corresponding to the salt tothe acid halide is between 1.00 and 1.17 or the mol ratio R_(b) of thehydroxyhydroperoxide corresponding to the hydroxyhydroperoxide salt tothe acid anhydride is between 1.00 and 1.17, (c) recovering saidperoxyester from step (b) so as to produce a final product, saidrecovery being conducted in the absence of an organic solvent, andwherein the hydroxyhydroperoxide is a hydroxy(tertiary-alkyl)hydroperoxide in which the hydroxyl group is situated in the 3 positionwith respect to the hydroperoxy group.
 5. A process according to claim 1wherein said recovery in the absence of an organic solvent comprisesconducting at least one aqueous wash of the peroxyester and decantingthe resultant aqueous phase from the resultant purified peroxyesterrs.6. A process according to claim 1 wherein said recovery in the absenceof an organic solvent comprises washing the peroxyester from step (b)with water, separating the resultant washed peroxyester with aqueouspotassium or sodium hydroxyl and decanting the resultant aqueous phasefrom the resultant washed peroxyester.
 7. A process for the preparationof a peroxyester said process comprising conducting the followingsequential steps: (a) reacting an hydroxyhydroperoxide with a base inthe absence of an organic solvent, and with a molar ratio R_(a) of thebase to the hydroperoxide of between 0.9 and 1.3, to obtain a salt ofthe hydroxyhydroperoxide, (b) on completion of step (a) reactingresultant salt of hydroxyhydroperoxide with an acid chloride to form aperoxyester, wherein the mol ratio R_(b) of the hydroxyhydroperoxidecorresponding to the salt to the acid halide is between 0.5 and 1.5, (c)recovering said peroxyester from step (b) so as to produce a finalproduct, said recovery being conducted in the absence of an organicsolvent, and wherein the hydroxyhydroperoxide is ahydroxy(tertiary-alkyl) hydroperoxide in which the hydroxyl group issituated in the 3 position with respect to the hydroperoxy group.
 8. Aprocess according to claim 1, wherein the hydroxyhydroperoxidecorresponds to the following formula:HO—C(R₃)(R₄)—CH₂—C(R₁)(R₂)—OOH in which: R₁ and R₂ are, independently ofone another, an alkyl having from 1 to 4 carbon atoms; R₃ and R₄ are,independently of one another, a hydrogen or an alkyl having from 1 to 4carbon atoms; R₁ and R₃ can be connected to one another via an alkylenebridge having 3 carbon atoms, this bridge optionally being substitutedby an alkyl having from 1 to 4 carbon atoms; and R₃ can additionally bea —CH₂—C(R₁)(R₂)—OOH group.
 9. A process according to claim 8, whereinthe hydroxyl(tertiary-alkyl)hydroperoxide is chosen from the groupconsisting of 3-hydroxy-1,1-dimethylpropyl, 3-hydroxy-1,1-dimethylbutyl,1-ethyl-3-hydroxy-1-methylpentyl, 1,1-diethyl-3-hydroxybutyl and5-hydroxy-1,3,3-trimethylcyclohexyl hydroperoxides.
 10. A processaccording to claim 1, wherein it is carried out in the absence of aphase transfer catalyst.
 11. A process according to claim 1, wherein thebase is KOH.
 12. A process according to claim 1, wherein said resultantsalt is reacted with said acid anhydride in the absence of an organicsolvent to form a peroxyester, said anhydride being chosen fromanhydrides of 2-methoxypropionic, isobutyric, tert-butyric, pivalic,2,2-dimethylbutyric, 2-ethylbutyric, hexanoic, neohexanoic, benzoic,heptanoic, neoheptanoic, 2-ethylhexanoic, octanoic, neooctanoic,2-phenoxypropanoic, 2-phenylpropanoic, nonanoic, isononanoic,neononanoic, 2-methyl-2-phenyl-propionic, 2-phenylbutyric, decanoic,neodecanoic, dodecanoic, 2-butyloctanoic, neododecanoic, undecanoic,neotridecanoic, methacrylic, methylcrotonic and 2 -methyl-2-butenoicacids.
 13. A process according to claim 1, wherein the reaction iscarried out between a hydroxyhydroperoxide salt and an acid halide. 14.A process according to claim 13, wherein the acid halide corresponds tothe formula R′COX, in which: R′ corresponds to one of the followingformulae:R₅R₆R₇C— and R₉CH═CR₈— in which: R₅ is a hydrogen or an alkyl havingfrom 1 to 8 carbon atoms; R₆ is an alkyl having from 1 to 8 carbonatoms; R₇ is an alkyl having from 1 to 8 carbon atoms, an alkenyl havingfrom 2 to 8 carbon atoms, an aryl having from 6 to 10 carbon atoms, analkoxy having from 1 to 6 carbon atoms or an aryloxy having from 6 to 10carbon atoms; R₈ and R₉ are, independently of one another, an alkylhaving from 1 to 4 carbon atoms; and X is a halogen.
 15. A processaccording to claim 14, characterized in that the halide is chosen from2-methoxypropionyl, isobutyroyl, tert-butyroyl, pivaloyl,2,2-dimethylbutyroyl, 2-ethylbutyroyl, hexanoyl, neohexanoyl, benzoyl,heptanoyl, neoheptanoyl, 2-ethylhexanoyl, octanoyl, neooctanoyl,2-phenoxypropanoyl, 2-phenylpropanoyl, nonanoyl, isononanoyl,neononanoyl, 2-methyl-2-phenylpropionyl, 2-phenylbutyroyl, decanoyl,neodecanoyl, dodecanoyl, 2-butyloctanoyl, neododecanoyl, undecanoyl,neotridecanoyl, methacryloyl, methylcrotonoyl and 2-methyl-2-butenoylhalides.
 16. A process according to claim 15, wherein the acid halide isan acid chloride.
 17. A process according to claim 16, wherein the acidhalide is neodecanoyl chloride.
 18. A process according to claim 1,wherein the ratio R_(b) is between 0.9 and 1.2.
 19. A process accordingto claim 1, wherein the hydroxyhydroperoxide is 3-hydroxy-1,1-dimethylbutyl hydroperoxide and the acid halide is neodecanoylchloride.
 20. A process according to claim 1, further comprising formingan aqueous emulsion comprising at least one peroxyester obtained by theprocess of claim
 1. 21. A process according to claim 1, furthercomprising conducting a polymerization process employing a radicalinitiator comprising at least one peroxyester obtained by the process ofclaim
 1. 22. A process according to claim 18, wherein the mol ratioR_(b) is between 1.00 and 1.16.